Aside from the fact that Niedzwiedz drove one of the Zakspeed cars and that they are the origin of the DJR cars I can't find a single thing about them anywhere on the web. Zakspeed was pritty much the Ford works team in the early 80's. Running the big Capris in the DRM, later on building the C100 prototype. They also ran the GTX Mustangs and GTP Probe GT in the IMSA Championship. Maybe they built those 2 cars as test cars for the new regulations and Ford Europe/Germany didn't approve of them racing a car that wasn't even available in Europe. I suspect Zakspeed could have entered some races of the Langstreckenpokal/VLN in 1983 to give the cars some testing under proper race conditions, but there are no results anywhere for those early seasons of the championship plus the Nürburgring was being rebuilt in 1983 so there wasn't that much racing going on there, for example the 24h race was cancelled.
A little jump in time to early 1987. Dick Johnson entered one of the cars in the Wellington 500 race sharing the car with Kiwi Robbie Ker. After a heavy crash they withdrew their entry and the car stayed with Ker, who kept using it for NZ Group A racing and at some point before 1989 rebuilt the car to "Sports Sedan" specs with wider wheelarches, etc.
The car then went through a whole bunch of hands until being bought by Ross Donnelly and rebuilt to original DJR specs by the same guy who built the two Pinepac Mustangs.
http://www.v8.co.nz/articles/ford-in...e-real-deal-42
One more picture of the Bert Moritz Mustang from 1988. Interesting field ...
Attached is a picture of the 2nd livery used by Gröpper in the 1987 DTM, which might have been just a repaint of the original CC car.